Bashar Assad addresses the newly elected parliament in Damascus (SANA/AP)

The Syrian president has vowed to "liberate" every inch of the country in the same way his troops recaptured the historic town of Palmyra from Islamic State earlier his year.

Bashar Assad's speech in front of the newly elected parliament came as government forces pushed ahead in their offensive in the northern province of Raqqa, the de facto capital of IS and the seat of its self-proclaimed caliphate.

Government forces have also almost encircled rebel-held neighbourhoods in Aleppo, Syria's largest city.

The situation on the ground is much better than it was months ago, Assad claimed, calling on the people "not to worry because the conditions are good".

Earlier, legislators had stood up and chanted, "Our soul, our blood we sacrifice for you, Bashar", as he walked into the parliament's main hall in central Damascus.

The scales of war in Syria have tipped in Assad's favour since Russia began an aerial campaign last September, helping government troops capture wide areas from insurgents. The biggest victory came in March when Syrian forces evicted IS from Palmyra.

"The way we liberated Palmyra and before that many areas, we will liberate every last bit of Syria from their hands. We have no choice but to be victorious," Assad said to applause from the deputies.

"Our war on terrorism will continue not because we like war. They imposed the war on us," Assad added, reiterating his staple blaming of foreign countries for Syria's five-year crisis. "The shedding of blood will not end until we uproot terrorism, wherever it is."

The speech was Assad's first before the newly elected chamber and his first public remarks since January. He thanked China for using its veto power at the UN Security Council months after the crisis began to prevent the imposition of sanctions on Syria. He also thanked Russia, Iran and Lebanon's Hezbollah group - three key allies that have played a critical role in turning the balance of power in his favour.

The Syrian president blamed the opposition for the failure of three rounds of indirect peace talks in Geneva this year, blasting his opponents as "traitors for foreign countries who have become mats for the feet of their masters".

The opposition demands that Assad play no part in any transitional or future political establishment in Syria. In Tuesday's speech, he rejected any changes in the constitution that could lead to the partitioning of Syria on a sectarian basis.

"A sectarian system turns the sons of the nation into enemies and foes," he said.